Yes, a standard PC IDE cable (40 wire) will work fine if using a 3.5" buffered interface in an A1200. You can also use the newer 80 wire IDE cables. I do in my A4000 and they work fine.

If however you wish to connect a cable directly to the A1200 IDE port you would need to use a 2.5" to 3.5" cable to convert from one to the other if a buffered IDE interface isn't being used. Also remember that 2.5" cables supply power the the HD, whereas for a 3.5" HD you need to power it from a separate 4pin molex power cable.